"Martina is really focused on her health and fitness. You wouldn't believe her muscles. She's 55 and she's fierce. Sports stars generally do well on the show and she's in tip-top shape," says Lifescript Entertainment Editor Mari Cartel, who interviewed the tennis champ.

Navratilova tells Lifescript how she's overcome many health scares. Her near-death experience climbing Mt. Kilimanjaro threatened her life even more severely than her breast cancer; she developed high-altitude pulmonary edema (fluid in the lungs) during the climb. Throughout her tennis career, she fought to rein in symptoms of arthritis.

Age certainly doesn't hold her back. Navratilova continued to win tennis matches and tournaments well after the age of 40. Now retired from professional tennis, Navratilova maintains a toned figure without working out. She shares her secret with Lifescript, "I don't train. I was in the gym [maybe] five times last year." Instead, she plays sports, rides her bicycle and runs.

The enviably fit tennis star told Lifescript it's no sweat dancing four hours straight in the studio with her "Dancing With the Stars" partner Tony Dovolani.

Next on her fitness to-do list? "I'm trying to elongate [my muscles]," she tells Lifescript.

Season 14 of "Dancing With the Stars" premiered Monday, March 19 on ABC.

ABOUT LIFESCRIPT: One of the fastest-growing online healthy living publishers, Lifescript.com attracts 6.3 million unique visitors monthly and is the only site focusing exclusively on women's health. More than seven million readers also subscribe to its six daily email newsletters. The company has offices in Mission Viejo and Beverly Hills, Calif., and in New York City.